The invention relates generally to an apparatus for mixing and dispensing a plurality of liquids and more particularly relates to a dispensing member for mixing a plurality of substances used in the formation of polyurethane foam.
In my U.S. Pat. No. 3,687,370 and my aforesaid patent application devices are disclosed for mixing and dispensing a plurality of liquids for forming polyurethane foam. The devices contain a mixing chamber for mixing a first liquid such as liquid organic resin, and a second liquid such as an isocyanate for forming polyurethane foam. The liquids were injected into the mixing chamber via a pair of aligned inlet ports positioned on opposed sides of the chamber. A reciprocating valving rod moved from a retracted position to an extended position to open the ports for liquid mixing and to close the inlet ports for preventing any further flow of liquid. When the valving rod moves from the extended to the retracted position the ports are open to permit liquid flow.
Since the liquid inlet ports into the mixing chamber of the prior foam dispensers were aligned with each other the flow pressure of one liquid was sometimes sufficient to cross-feed into the inlet port for the other liquid. Frequently when cross-feed occurred, a reaction caused the two liquids in the inlet port to coagulate, which eventually hardened, and either partially or completely blocked liquid flow into the mixing chamber. The cleaning fluid carried by the valving rod to dissolve any hardened or foamed substance remaining in the mixing chamber could not penetrate the inlet ports to dissolve any blockage building up therein. Such obstruction disrupted further use of the gun until the barrel assembly was disassembled and the hardened substance removed from the inlet port(s).
The present invention is an improvement over the prior dispensing devices of my above noted patent and patent application in that I now form the liquid entry ports so that one is spaced forward or upstream from the other. This prevents undesirable cross-feeding across the mixing chamber from one liquid entry port into the other liquid entry port. Such construction also now permits higher operating pressures at the ports to assure better mixing of the two chemicals.
In an embodiment of the present invention a dispensing apparatus includes a tubular member having a pair of liquid entry ports formed spaced apart therein, with one such port positioned forward with respect to the other. The inside of the tubular member defines the mixing chamber. A pair of liquid input passageways are aligned with each other, and each passageway communicates with one of the entry ports for ejecting a liquid into the mixing chamber. The cross-sectional areas of the liquid passageways are substantially greater than the cross-sectional areas of the ports, so that the tubular member is insertable into the dispensing gun whereby either entry port communicates with either of the liquid input passageways.